In recent years, the value of keeping electronic medical records in place of paper records has been widely recognized in the health care industry. The use of electronic medical records allows health care providers and patients to store, retrieve, and share medical information with considerably more ease and accuracy. The sharing of medical information is particularly important in treatment programs involving the injection of insulin, human growth hormone, or other medications.
Typically, these injections are performed using disposable syringes. Unfortunately, no adequate apparatus exists that measures and electronically records dose information from a disposable syringe. As a result, the patient or health care worker performing the injection is burdened with the task of injecting the dose and then manually recording the dose amount in a log book.
Because of the frequency of such injections, often several times a day for diabetics, it becomes difficult for a patient to keep accurate records. Indeed, studies have shown that a patient's own records and recollections are often incomplete and inaccurate. Additionally, a patient may intentionally cheat while making self-recorded entries in an attempt to create a log book that will please his or her doctor. In the long-term this makes patient monitoring extremely difficult and jeopardizes the treatment program, possibly even endangering the patient's life.
Attempts have been made at developing electronic management systems for assisting patients in self-administered drug programs. For example, U.S. Pat. No. 5,019,974 issued to Beckers describes a hand-held, microprocessor-based recorder that interfaces with a master computer. The patient enters therapy information into the recorder via a keyboard. The recorder includes a display for displaying treatment therapy guidelines to the patient. The recorder also has a blood glucose meter for recording the patient's blood glucose levels.
The recorder described by Beckers does not automatically measure and record dose information from a disposable syringe. After injecting a dose, the patient must manually enter the dose information into the recorder using switches or keys. Although this is an improvement over keeping written records on paper, the effectiveness of the drug program is still limited by the patient's recollections and recordings, which are unreliable.
Attempts have also been made at developing devices that deliver a predetermined dose of medication and record the dose amount. For example, U.S. Pat. No. 5,176,502 issued to Sanderson et al. on Jan. 5, 1993 describes a syringe pump for expelling a preset dose of medication from a syringe. The syringe pump includes a syringe retainer for holding the syringe and a driver for engaging the plunger of the syringe. An electric motor pushes the driver and plunger into the syringe barrel to expel the medication.
The syringe pump further includes a monitoring circuit for monitoring the motion of the driver during the delivery of the medication. The monitoring circuit includes a linear potentiometer having an electrically conductive strip of resistive material. The resistive material is positioned such that it engages an electrical contact of the driver. The position of the electrical contact on the resistive strip varies the voltage of the monitoring circuit, thus indicating the position of the plunger inside the barrel. A microprocessor receives voltage signals from the monitoring circuit and compares the voltage signals to preprogrammed signals to determine if the plunger displacement corresponds to correct displacement for delivering the preset dose. A control mechanism connected to the microprocessor regulates the driver's movement to ensure the preset dose of medication is delivered.
Although the syringe pump described by Sanderson does allow electronic recording of dose information, it is only designed to deliver medication directly into an intravenous line. It is not designed to inject a patient directly nor can it measure and record a dose from a syringe unless the syringe pump pushes the plunger. Consequently, the syringe pump is of little use to a health care worker who must inject a patient directly, or to an outpatient who must follow a self-injection treatment program.
Another device for injecting a preset dose of medication and for recording the injected dose is disclosed in U.S. Pat. No. 4,950,246 issued to Muller on Aug. 21, 1990. Muller describes a battery-operated injection pen having a pump rod driven by an electric motor. The electric motor is controlled by an electronic control unit that includes a microprocessor with a memory for storing dose information. The injection pen further includes a sensor connected to the control unit for electrically determining the position of the pump rod, and thus the amount of medication injected.
Although the injection pen described by Muller measures and electronically records dose information, it has several disadvantages that have precluded its widespread use. The injection pen is an expensive device requiring complicated electronic equipment to deliver and record doses. Moreover, because the injection pen integrates a syringe and electronic recorder into one device, it is not disposable. The patient must use it repeatedly for each injection, even after the injection pen has been contaminated with blood. Consequently, the injection pen does not provide an inexpensive, convenient, or hygienic solution to patients wishing to measure and electronically record injected dose information.
U.S. Pat. No. 4,853,521 issued to Ronald Claeys on Aug. 1, 1989 presents a programmable, intelligent reader unit which receives and records drug data using hand-held or fixed scanners. The scanners read bar codes in place on syringes, ampules, flow meters, etc. In addition, this intelligent reader allows the user to weigh a syringe before and after injection to determine and record the administered amount of medicine. Dosage data logged in this manner can be displayed or printed out in the form of a record.
Operating the device described by Ronald Claeys requires many complicated steps of weighing syringes, scanning in bar codes, etc. The complexity of the required procedures as well as the high cost of the apparatus have precluded its widespread use. Additionally, the device cannot be easily carried by the user for recording doses while away from the health care facility or home. Thus, no inexpensive apparatus exists for determining and electronically recording dose information from a disposable syringe. Further, no such apparatus exists that is both simple in operation and easily carried by a user.